Recent research on nutcracker syndrome has focused mainly on exploring the value and criteria of various imaging modalities for the diagnosis of the disease. Providing more quantitative parameters related to the lesion through non-invasive modalities has been a focus of studies on clinical diagnosis and treatment of nutcracker syndrome. However, no relevant data are available on pressure changes in left renal vein and inferior vena cava and hemodynamic parameters in left renal due to different degrees of stenosis in the left renal vein.

To develop acomputational fluid dynamics (CFD) model to obtain the hemodynamics of individuals with nutcracker syndrome, to explore the relationship of blood flow velocity, wall static pressure, and wall shear stress with the change of vessel disease.

70 patients with nutcracker syndrome were sampled from the Affiliated Hospital of Xuzhou Medical University from September 2019 to March 2021. CFD was used to simulate the intravascular blood flow in the left renal vein of real-world patients with nutcracker syndrome based on CT enhanced images. The hemodynamic characteristics, including vascular diameter and flow velocity, were obtained and compared with those measured by ultrasound.

The left renal vein's intake pressure was high, but the stenosis and exit pressures were low. From the inlet to the outlet, the pressure successively dropped. Except for the narrow region, the wall shear stress was smaller, and the closer to the center of the stenosis, the higher the shear stress. The blood flow velocity in the stenosis was significantly higher than that in other areas of the left renal vein, which was consistent with the result of ultrasonography.

The successfully developed vascular model, The hemodynamic change rules of nutcracker syndrome patients include that the inner diameter of the left renal vein becomes smaller and the flow velocity increases at the stenosis.